It is known in the an to provide a reinforcing beam in vehicle doors to protect the vehicle occupants from a side impact from other vehicles. Typically, it is highly desirable in such situations that the beam be as strong as possible at the least possible weight to provide maximum protection to the vehicle occupant from side impact. Strength of the side impact beam and door structure should be of such a magnitude that deformation of the side impact beam and the vehicle door meets the requirements for door strength in side impacts as found by a review of Federal Motor Vehicle Safety Standard (FMVSS) 214.
To provide for the protection of vehicle occupants in frontal impacts, vehicles must meet the standards of FMVSS 208 (occupant injury in 30 mph barrier test), which determines how much energy the front of the vehicle must absorb in deformation. Automotive vehicles have become more aerodynamic to help meet federally-mandated fuel economy ratings to enhance the environment. One method of achieving greater aerodynamics is lowering the from hood. Additionally, thinner sheet metal and more polymers are being utilized instead of previous heavier gauge steel. Therefore, to meet the FMVSS requirements, more energy must be absorbed in the vehicle doors.
When energy absorption additionally requires deformation of the door structure, it has been found that such energy absorption is limited by the column stiffness of the side impact beam. Therefore, it is desirable to provide a door structure having a rigid impact beam which can maximize side impact strength while at the same time allowing the door structure to absorb energy absorption mode in a frontal impact of the vehicle.